In modern warehousing operations, it is common to employ storage racks extending in rows with sufficient aisle space between to permit deployment of automatic stacker cranes or operator driven vehicles. In either case, the cranes or the vehicles must be capable of moving materials between the ground level and the uppermost racks. Where operator controlled vehicles are used, it is common for the vehicles to have on-board batteries for propelling the vehicles along the floor between aisles. Electrical energy for raising and lowering, loads, however, is supplied from an overhead electrical rail system usually supplying three phase electrical power at a voltage for 460 volts. The problem arises when such vehicles are to be moved from one aisle to another requiring removal of the trolley from contact with the rails in one aisle and re-establishing contact with the rails in the next aisle. The problem is particularly acute where the height of the rails above the operator of the vehicle may be of the order of 60 feet.
One approach to the problem is disclosed in U.S. Pat. No. 4,194,603 of Mar. 25, 1980. In that patent, the ends of the trolley rails are bent upwardly and the rail structure and housing terminates in an outwardly tapered insulating end fitting. A pair of horizontally spaced guide members extend upwardly from the uppermost surface of the trolley, the spacing being substantially equal to the horizontal dimension of the rail housing structure. The theory is that the operator need only position these guide members to straddle the tapered "nose cone" and further advancement will serve to align the trolley with the elevated end portions of the rail. The difficulty is that there is insufficient tolerance for horizontal alignment in view of the vertical distance between the vehicle and the rails so that while the approach shown in this patent is an improvement over no guide structure at all, it still is not a complete answer to the problem.